Tissue repair or reinforcing implants, such as meshes, may be designed to enable tissue in-growth on one side (e.g., by having open pores or interstices) and resist tissue in-growth on the opposing side (e.g., by having a smooth surface such as a film or non-porous layer, conventionally referred to in this art as an adhesion barrier). This is important when the mesh implants are used or implanted in the abdominal area, for example in hernia repair procedures, where adhesion of the peritoneum (i.e., tissue ingrowth) to the implant is desired while tissue in-growth or adhesions on the visceral side is unwanted (i.e., anti-adhesion). Several conventional products are known in this art and commercially available having one basically smooth side which is an adhesion barrier and one porous or rough side for tissue in-growth. The products may be completely absorbable, completely non-absorbable, or partially absorbable and partially non-absorbable. The products may be composites of multiple mesh layers and adhesion resistant barriers. Certain implants are ready for use out of the package (e.g., Proceed® Hernia Mesh, Gore DualMesh®, and Bard Composix® Mesh) and other mesh implants are required to be pre-soaked for several minutes in water or saline solution prior to implantation in order to swell the adhesion barrier and make the implant sufficiently soft for implantation and placement in the patient (e.g., Sepramesh®; Parietex® Composite).
In certain surgical applications, it is desirable for these implants to deliver a dose of therapeutic or active agent to the tissues surrounding or adjacent to the implant. To achieve this, the implant may be preloaded by coating or otherwise impregnating with the desired active agent by the manufacturer prior to packaging. However, preloading an implant with an active agent can be difficult. In addition, the amount of active agent that can be added to the implant is limited unless the active agent is delivered in a controlled release manner by the implant for controlled release to the adjacent tissues. To enable the release of stored active agent on both sides of an implant, the implant's active agent reservoir must have fluid communication with each side of the implant. In the case of an implant consisting of a mesh contained between opposed outer film layers, this can be made possible by including pores within the films on both sides of the mesh. However, providing such pores may allow tissue-to-tissue contact through the pores located in the films in those areas where the films are laminated to each other and the pores are in alignment. Tissue-to-tissue contact will encourage or permit unwanted tissue adhesions. If pores are present in only one film layer of the implant, the therapeutic fluid may not be effectively exposed to the side without any pores. It is also believed that having pores on only one side will limit tissue fluid flow between the two sides of the implant. This may result in seroma formation.
A conventional way to deliver active agents in conjunction with implanted medical devices is for the surgeon or assistant to dip or soak the medical device in a solution of the active agent prior to implantation. As an example, dipping surgical hernia mesh film constructs in active agent solutions is important to provide an active-loaded mesh that may also be placed in contact with the viscera to prevent adhesions. In other applications there may be a need to place the fabric in contact with the vaginal wall (e.g., a pelvic mesh) or in contact with the urethra such as with the GYNECARE® TVT system from Ethicon, Inc., wherein a perforated film assembly could be beneficial to prevent erosion of structures like the bladder, vaginal wall, etc. by a part of the implant. Currently marketed and commercially available products that are coated with collagen films (e.g., Parietex®Composite (PCO) MESH) have to be incubated for 5-10 minutes in a solution of active agent, which is relatively time consuming task to perform when in an operating room (OR) setting and while the patient is under anesthesia during a procedure. A further drawback with current commercially available products is that the active agent coatings are very sensitive to mechanical forces during handling in the operating room, and using forceps to manipulate or place the implants can easily destroy such coatings and may lead to disintegration of the product. Certain commercially available mesh composite implants such as Composix® mesh, have a polypropylene mesh with an ePTFE layer on one side of the mesh. Since both polypropylene and ePTFE both do not accept hydrophilic liquids very well, it is anticipated that the delivery of such meshes along with a coating solution of active ingredient through a trocar to the surgical site would be difficult.
WO2003041613 A1 describes meshes having two synthetic polymer films on each side, wherein the films are glued or welded in the pores of the mesh together; neither perforated pore-containing films on both sides nor offset pore-containing films are described.
EP1237588 B1 describes a non-absorbable mesh implant covered on one side with an absorbable film made from natural (hyaluronic acid) or natural-derived (CMC) materials which may have pores, and in between an adhesive such as a polylactide co-polymer. A drug may be incorporated in any portion of the prosthesis to provide for controlled release of the drug into the body.
WO2003099160 A1 describes knobbed films that may be present on both sides of a fabric implant, wherein both films can have holes that are arranged in a pattern. Filling the knobs with an active agent is taught, however dipping or filling the area outside the knobs is not indicated.
EP 1541183 A1 describes a mesh having absorbable polymer films with two different absorption times. US20030017775 A1 describes a composite intraluminal prosthesis which is preferably used as a vascular prosthesis and includes a layer of ePTFE and a layer of textile material, which are secured together by an elastomeric bonding agent. The ePTFE layer includes a porous microstructure defined by nodes interconnected by fibrils. The adhesive bonding agent is preferably applied in solution so that the bonding agent enters the pores of the microstructure of the ePTFE.
There is a need in this art for tissue implant devices that offer advantages over the tissue devices of the prior art, including providing a device that permits rapid absorption of active agents while providing tissue separating properties at least for a certain period of time. In particular, tissue implants are needed that are well suited to fast dip coating processes for providing active implants with effective amounts of active agents in a quick and efficient manner, particularly for dipping in the operating room. Also needed are fast, dippable mesh-laminate implants suitable for an inline process (pulling through a coating bath), wherein the impregnation time of the active agent into the mesh implant is reduced.